The present invention relates generally to a method, apparatus and system for mitigating in-band signaling noise, such as robbed-bit signaling noise.
Telephony network architectures allow for the possibility of multiple paths between end users which may incorporate one or more digital trunk links (Bellcore TR 008 and GR 303 compliant interface standards) which may use in-band signaling, such as robbed-bit signaling (RBS) for call supervision or management.
New network architectures (hybrid fiber coaxial cable (HFC) access, digital loop carrier (DLC) access, wide area network (WAN) access, voice over internet protocol (VoIP) access, etc.) add to the possibility of in-band signaling links by placing remote terminal access nodes in close proximity to service locations. Some of these remote access network nodes also utilize digital trunk links to back haul the local access node traffic to a central office switch. Some of these trunk links also utilize in-band signaling.
In-band signaling, such as RBS, removes informational content from the least significant bit of every sixth pulse code modulated (PCM) sample from a 64 kilobits-per-second (kbps) traffic channel and replaces it with network signaling information. This RBS network signaling information is only used by the network and therefore, represents errors to the traffic channel. This network signaling therefore represents informational errors or xe2x80x9cnoisexe2x80x9d (RBS noise pattern).
Some modems detect in-band signaling as degradation in the signal-to-noise ratio (SNR) in a 64 kbps traffic channel and step down the transmission rate to compensate for the SNR degradation. Newer modems utilize a unique communication protocol (ITU-T V.90) in the downstream path (from local digital switch to subscriber premises) which utilizes digital channel coding in the PCM domain. The RBS affect on these modems is more significant in that the RBS corrupts the digital channel coding which results in a greater impact on the transmission rate and the block error rate (BLER) than simple SNR degradation.
While some of these modems are capable of detecting the affects of RBS and can alter the channel coding to optimize the transmission rate and minimize the BLER degradation, other modems are unable to detect the RBS and fail to adapt the channel coding to compensate.
Thus, there exists a need for a method, apparatus and system for mitigating in-band signaling noise.